A time control is a mechanism in the tournament play of almost all two-player board games so that each round of the match can finish in a timely way and the tournament can proceed. Time controls are typically enforced by means of a game clock. Time pressure (or time trouble or zeitnot) is the situation of having very little time on a player's clock to complete his remaining moves.
The World Chess Federation FIDE sets a single time control for all major FIDE events according to the handbook: 90 minutes for the first 40 moves followed by 30 minutes for the rest of the game with an addition of 30 seconds per move starting from move one. Exceptions can be made though, the Candidates tournaments for the World Championship have been played at 120 minutes for 40 moves, followed by 60 minutes for 20 moves, followed by 15 minutes for the rest of the game, with a 30 second increment starting on move 61.
The amount of time given to each player to complete their moves will vary from game to game. However most games tend to change the classification of tournaments according to the length of time given to the players. Shorter time limits, which do not afford due consideration to moves, are afforded a lesser degree of importance. Indeed shorter limits are normally given special names to distinguish them.
'Lightning' is the quickest limit, then 'blitz'. Chess has an 'active' category after this. In chess, Lightning refers to 3 minutes or below, blitz refers to between 4 and 15 minutes, and Active is between 15 and 30. By way of contrast, for Go anything under twenty minutes could be considered blitz. In terms of chess ratings, 30 minutes is considered to be both blitz (fast chess) and long (slow chess) at the same time as it affects both ratings.
The exact approach to using a game clock to regulate games varies considerably.
Sudden death 
This is the simplest methodology. Once a player's main time expires, he loses the game.
Each player's clock starts with a specified time (e.g. 1 minute, 10 min etc.). While Player 1 is deciding on their move, their clock time is decreasing and Player 2's clock time is increasing. This is similar to how an hourglass works; sand empties from one container and fills into the other. Moving slowly gives your opponent extra time. The sum of both clocks will always remain the same. There is no maximum amount of time allotted for a game with this timing method; as long as both players play quickly, the game will continue until its natural end. When time runs out on one player's clock the game is over and that player loses. This is very uncommon to be used in chess tournaments outside of certain websites.
Overtime formats 
Here the game time is separated into two basic domains: the main time, and the overtime. To switch between the two requires some trigger event. Often this is the expiration of the main time. In chess, reaching a fixed number of moves can trigger the gain of a fixed amount of bonus time. This is the general chess rule and it usually occurs in long games after the 40th move.
||It has been suggested that Byoyomi be merged into this article. (Discuss) Proposed since September 2011.|
In go two common forms are:
Japanese byo-yomi 
After the main time is depleted, a player has a certain number of periods (for example five periods, each of thirty seconds). If a move is completed before the time expires, the time period resets and restarts the next turn. Now if a move is not completed within a time period, the time period will expire, and the next time period begins. This is written as <maintime> + <number of byo-yomi time periods> of <byo-yomi time period>. Using up the last period means that the player has lost on time. In some systems, such as certain Go title matches, there is no main time; instead, the time used is rounded down to the nearest whole increment, such as one minute, and the actual counting of time occurs toward the end of one player's time. (The term byoyomi literally means "counting the seconds [out loud].")
Canadian overtime 
After using all of his/her main time, a player must make a certain number of moves within a certain period of time — for example, twenty moves within five minutes. Typically, players stop the clock, and the player in overtime counts out the required number of stones and sets the remaining stones out of reach so as not to become confused, whilst the opponent sets the clock to the overtime period. If all the moves are made in time, then another period of overtime starts — another set of stones and the timer again reset to the overtime period. If all the moves are not made in time, the player has lost on time. This is written as <main time> + <number of moves to be completed in each time period> in
- "Rules & regulations for the Candidates Tournament of the FIDE World Championship cycle 2011-2013". FIDE. Retrieved 8 May 2013.
- http://pages.infinit.net/steven/byoyomi.htm The Origins of Canadian Byo-Yomi
- http://www.britgo.org/rules/approved.html BGA Rules page
- http://www.usgo.org/resources/KSS.html "Ing's SST Laws of Go"
- http://www.scrabble-assoc.com/build/rules/rules2.html#r3c2 "NSA Official Tournament Rules", National Scrabble Association
- FIDE Tournament Time Control rule
- US Patent No. 4,884,255 for Fischer's clock
- Game time controls on BrainKing
- A sudden death time control determines the 2008 U.S. Women's Chess Championship